1. Rest in Peace Paul (Kegger) If you would like to help the family in this time of great sorrow and need, you may donate on their GoFundme page: https://www.gofundme.com/mckechnie-medical-and-funeral-fund?
    Dismiss Notice

SX-626 Wrong Cap and other Questions

Discussion in 'Pioneer Audio' started by moondogtn, May 9, 2017.

  1. moondogtn

    moondogtn AK Subscriber Subscriber

    Messages:
    321
    Location:
    Pleasanton, TX
    Ok....so, I decided to go ahead and try to finish up this little project. All was working before I decided to go ahead and replaced the remainder of transitors on power amp board. Q1-Q8, used list I provived initially.....and during alignment noticed voltage was off (showed 24 VDC) on Q11 case. Upon further investigation, I notice 2sc2690 I had installed in Q5 was backward. I removed and installed correctly, voltage was now correct on both channels but no sound (very faint) out of right channel, actually there is sound but very faint??? I went ahead and went through alignment. VR1 and VR2 set to 28.5 which is half of my collector voltage on Q9. and Q10 respectively. I also checked dc offset and set to 17mV. Still nothing out of right side. There is some sound but very, very, faint. So, I went through and checked things again. Still am not finding anything blatantly wrong. I checked volages on Q5 and Q6 and they seem fine as well? Any ideas? I may have lost a component or???

    Bill
     
  2. moondogtn

    moondogtn AK Subscriber Subscriber

    Messages:
    321
    Location:
    Pleasanton, TX
    I have been busy with school and work so haven't had much time to dedicate to this. I can post up voltages at different test points if that would help. I hope to try and connect to another receiver using preamps just to confirm issue is with power amp board. Thanks for any advice of this.

    Bill
     
  3. moondogtn

    moondogtn AK Subscriber Subscriber

    Messages:
    321
    Location:
    Pleasanton, TX
    I hooked up the preamp out to another amp and all is good. So, this means something on my power amp board is causing the issue, correct? I am going to go back through and see if I can determine what is bad on that channel.
    Any thoughts on things to check as it was working prior to installation of Q1 through 8.

    Bill
     
  4. goat67

    goat67 AK Subscriber Subscriber

    Messages:
    3,009
    Location:
    Twin Cities MN
    Lets see it was working and then you installed Q1 - Q8 and it quit working.... hmm maybe something wrong with the work you did installing Q1-Q8?
    Verify each transistors pins and how they are installed. Test each one or better yet replace them again but install them correctly.

    Another thing to do is compare the voltages from the good side to the bad side to identify the bad component
     
  5. moondogtn

    moondogtn AK Subscriber Subscriber

    Messages:
    321
    Location:
    Pleasanton, TX
    Goat, I appreciate the suggestions and will recheck tonight but I have done all that as I am sure it had to be the last work I did or maybe a component.

    My question may have been poorly worded. What I am asking is regarding the likelihood that I lost or killed a component? Maybe when I installed Q5 with wrong orientation? Or maybe one of those loose bias wires touched something.

    I am still digging into it but just trying to figure out where to look next.

    My voltages seem comparable but I will check those again and post findings if I don't come up with a solution. Thanks again.

    Bill
     
  6. goat67

    goat67 AK Subscriber Subscriber

    Messages:
    3,009
    Location:
    Twin Cities MN
    Something is bad in the circuit. You have one channel that works. You can check each and every component one by one or you can trouble shoot this by verifying the voltages.
    Worse comes to worse swap a component one at a time between channels as a last resort.
    Lift a leg of R23 R25 R27 R29 R31 R33 and ohm these out
    Pull Q9 Q11 and test these

    So measure the voltages at each Transistor

    Q1
    E
    B
    C
     

Share This Page